In the process of building construction, the building surfaces, including walls and roots, are commonly covered in some type of membrane, barrier or building wrap before the final exterior surface, for example, shingles, siding or stucco, is applied. The building barrier or wrap serves to protect the structure of the house from the weather, especially moisture which may seep past the final exterior surface, e.g., the shingles or siding.
Conventionally, roofing barriers (“underlayments”, so called as they ‘underlay’ the final roof treatment of, e.g., shingle or tile) are applied to the surface of the roof (usually plywood) using a separately applied adhesive. In conventional practice, the underlayments are supplied to the builder in rolls. To install, installers employ a two step process. First, a layer of uncured or wet adhesive is manually applied to the roof surface by the installer with a roller, brush or mop-like tool. Subsequently, the underlayment is unrolled and applied over the adhesive layer; pressure and/or heat may be subsequently applied to ensure drying/curing of the adhesive and adherence of the underlayment to the roof surface.
In addition, because most roofs have a greater surface area than the underlayment sheet, more than one sheet is required to cover a roof. In conventional practice, to ensure that the seams between the adjacent sheets are waterproof, the ends of the sheets are overlapped by spreading an adhesive along the outer edge of the first sheet, and overlying the edge of the second sheet onto the adhesive coated portion of the first sheet. Alternatively (or additionally), the seams are taped with specially devised asphalt-containing roof seam tapes.
This method suffers from several drawbacks. The first two steps must be carried out in rapid succession so the adhesive does not cure or dry before the underlayment is applied. This presents a challenge on sunny, warm or windy days, when the adhesive dries very quickly.
Because the adhesive is manually applied both to the bottom surfaces of the sheets and to the edges, the thickness and/or continuity of adhesive may vary from roof to roof, or even from sheet to sheet on the same roof, resulting in inconsistent performance of the underlayment and variable material costs.
Moreover, the multi step installation process (including the adhering and/or taping of the seams) is time intensive, resulting in greater labor costs as compared to, for example, a one step process, and involve increased time spent on rooftop by installers, which gives rise to an increased chance of injury.
Prior art attempts to alter the structure of the underlayment sheet so that the installation process is streamlined have been attempted, but these attempts have drawbacks.
For example, U.S. Pat. No. 6,924,015 describes a roofing membrane having an upper layer of a specifically defined modified bituminous material and a side lap coated with factory applied adhesive covered with a release film, and a lower layer carrying a self adhesive bituminous material and a release film.
U.S. Pat. Nos. 7,132,143 and 6,696,125 describe a “dual compound”, self-adhering underlayment or roof covering wherein the back side bears a specifically defined asphalt containing self-adhesive that adheres to a roof surface; this back side is covered with a release liner which is removed and discarded at installation. The front side has a defined side lap and end lap; the whole of the front side is coated with a polypropylene-based top layer and the lap ends are covered with a release sheet, while the remainder of the front side is covered with a surface agent, such as a stitch bonded fabric.
In each of these described technologies, the installer must remove both the release liner from the back side, and from the front side to expose the adhesives, adding extra steps, risk and inconvenience to the task of installation.
Thus, there remains a need in the art, for an effective roof barrier or underlayment that is simple and quick to install, and yet which maintains high performance standards.